Process for producing polymeric glove, which has different properties at outer and inner layers, and polymeric glove produced by same process

ABSTRACT

A polymeric glove is made by a process wherein a glove form is dipped into a first bath containing a solvent and a first polymer, which when solidified has a first property, and the first polymer is solidified, wherein the glove form, on which the first polymer has solidified, is dipped into a second bath containing a solvent and a second polymer, which when solidified has a second property differing from the first property, and the second polymer is solidified, and wherein what results is stripped from the glove form, so as to invert what results. The polymeric glove has an outer layer having the first property, an inner layer having the second property, and an intermediate, transitional layer. The first property may be a comparatively higher coefficient of friction of an outer surface, which is defined by the outer layer, or may be a comparatively lower stiffness or a comparatively greater elasticity. The second property may be a comparatively lower coefficient of friction of an inner surface which is defined by the inner layer, or may be a comparatively higher stiffness or a comparatively lesser elasticity.

TECHNICAL FIELD OF THE INVENTION

[0001] This invention pertains to a process for producing a polymeric glove, such as a polyurethane glove useful in a clean room, in which semiconductors are being handled. Further, this invention pertains to a polymeric glove, which is produced by the process.

BACKGROUND OF THE INVENTION

[0002] Commonly, polymeric gloves useful in clean rooms, in which semiconductors are being handled, are produced from polyurethanes, which in certain formulations have comparatively higher stiffness but comparatively lower coefficients of friction but which in other formulations have comparatively lower stiffness but comparatively higher coefficients of friction. Whenever used herein, the term “stiffness” is intended as a singular term or as a plural term, as the context requires or permits.

[0003] Polyurethane gloves of those formulations having comparatively higher stiffness and having comparatively lower elasticity but having comparatively lower coefficients of friction tend to be comparatively easier to don and to doff but to be comparatively less comfortable to wear. Polyurethane gloves of those formulations having comparatively lower stiffness and having comparatively higher elasticity but having comparatively higher coefficients of friction tend to be comparatively harder to don and to doff but to be comparatively more comfortable to wear.

[0004] Various processes are known, whereby to modify polyurethane gloves of those formulations having comparatively lower stiffness but having comparatively higher coefficients of friction, so as to become meaningfully easier to don and to doff. One known process is powdering, which is unacceptable for polyurethane gloves used in clean rooms, as talcum and other powders are regarded as contaminants in clean rooms and as irritants to glove wearers.

[0005] Another such process is quenching in steam or in water, as a liquid, whereby to displace superficially retained solvent with water. Quenching has shortcomings, however, as quenching can degrade polyurethane gloves and produces waste streams, which must be properly disposed of or which must be properly recycled. Other known processes, which include so-called “case-hardening” processes, employ chemical treatments, such as chlorination, which have similar shortcomings and which can leave behind harmful chemical residues. Other known processes involve coatings, which are applied to polyurethane gloves after their production, at physical interfaces, which can exhibit mechanical weaknesses and at which flaking or cracking can occur.

SUMMARY OF THE INVENTION

[0006] This invention provides a process for producing a polymeric glove, which has an outer layer having a first property, an inner layer having a second property differing from the first property, and an intermediate, transitional layer. The first property may be a comparatively lower stiffness and the second property may be a comparatively higher stiffness. The first property may be a comparatively higher coefficient of friction of an outer surface, which is defined by the outer layer, and the second property may be a comparatively lower coefficient of friction of an inner surface, which is defined by the inner layer. The first property may be a comparatively greater elasticity and the second property may be a comparatively lesser elasticity.

[0007] The process comprises initial steps of dipping a glove form into a first bath containing a solvent and a first polymer, which when solidified has the first property, and solidifying the first polymer, further steps of dipping the glove form, on which the first polymer has solidified, into a second bath containing a solvent and a second polymer, which when solidified has the second property, and solidifying the second polymer, and a further step of stripping what results from the preceding steps, from the glove form, so as to invert what results therefrom. The solvent of the second batch must be capable of solubalizing the first polymer as well as of solubalizing the second polymer.

[0008] Preferably, the solvent of the first bath and the solvent of the second bath are similar. Preferably, the first and second polymers are polyurethanes. In a preferred mode for carrying out this invention, the first and second polymers are polyurethanes, the solvent of the first bath and the solvent of the second bath are similar, each being dimethyl acetimide or dimethyl formamide, the first bath comprises approximately 16% by weight of the first polymer, and the second bath comprises approximately 8% by weight of the second polymer.

[0009] The polymer selected for the inner layer may be selected specifically for wearer-associated properties, such as ease of donning, wearer comfort, and biocompatability, whereas the polymer selected for the outer layer may be selected for physical properties, such as grip, strength, elasticity, and cleanliness. The process provided by this invention may be carried out so that the properties of the outer layer predominate in the finished glove or so that the properties of the inner layer predominate in the finished glove. The process provided by this invention produces a transitional layer, which has a blend of the properties of the inner and outer layers.

[0010] Whenever used herein, the term “solidifying” is intended to encompass curing a polymer, if and when curing is necessary to solidify the polymer from a solution, and to encompass drying a polymer, if and when drying is sufficient to solidify the polymer from a solution. It is recognized that drying so as to produce hydrogen bonds may be also regarded as curing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a simplified, plan view of a polyurethane glove, which has been made by the process provided by this invention.

[0012]FIG. 2, on a larger scale, is a simplified, sectional detail taken along line 2-2 of FIG. 1, in a direction indicated by arrows.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

[0013] As illustrated, a polyurethane glove 10 is made by the process provided by this invention, whereby the polyurethane glove 10 has an outer layer 12, which has a first set of properties, an inner layer 14, which has a second set of properties, and an intermediate, transitional layer 16, which does not have sharply defined interfaces with the outer and inner layers 12, 14, and which has blended properties from the first and second set of properties. In FIG. 2, the apparent interfaces between the intermediate, transitional layer 16 and the outer and inner layers 12, 14, are illustrative only and are not intended to suggest sharply defined interfaces. The first set of properties include a comparatively lower stiffness, a comparatively higher elasticity, and a comparatively higher coefficient of friction of an outer surface, which is defined by the outer layer 12. The second set of properties include a comparatively higher stiffness, a comparatively lower elasticity, and a comparatively lower coefficient of friction of an inner surface, which is defined by the inner layer 14.

[0014] The process comprises initial steps of dipping a glove form into a first bath containing a solvent and a first polymer, which when solidified has the first property, and solidifying the first polymer, further steps of dipping the glove form, on which the first polymer has solidified, into a second bath containing a solvent and a second polymer, which when solidified has the second property, and solidifying the second polymer, and a further step of stripping what results from the preceding steps, from the glove form, so as to invert what results therefrom. The solvent of the second batch must be capable of solubalizing the first polymer as well as of solubalizing the second polymer.

[0015] Preferably, the solvent of the first bath and the solvent of the second bath are similar. Preferably, the first and second polymers are polyurethanes. In a preferred mode for carrying out this invention, the solvent of the first bath and the solvent of the second bath are similar, each being dimethyl acetimide or dimethyl formamide.

[0016] In the preferred mode for carrying out this invention, the first polymer is a segmented polyurethane urea, which is available commercially from E. I. DuPont deNemours & Co. of Wilmington, Del., under its “D10M” trade designation, and is regarded as adhesive, when its coefficient of friction is measured in a manner described below. In the preferred mode for carrying out this invention, the second polymer is a segmented polyurethane urea, which is available commercially from E. I. DuPont deNemours & Co. of Wilmington, Del., under its “D10M-A” trade designation, and provides a coefficient of friction of approximately seven to eight inches, as measured in the same manner.

[0017] Two examples of possible conditions for carrying out the process provided by this invention are set forth below, each utilizing dimethyl acetimide as the solvent in each batch and each utilizing the DuPont polyurethanes specified in the preceding paragraph. In each example, dipping times are divided into form insertion, dwell, and form retraction times, which are controlled separately. Process Variable Bath 1 Bath 2 Example 1 DuPont Polyurethane D10M D10M-A Bath Temperature (° C.) 30 ± 5  30 ± 5  Percentage of Solids 14 ± 1  9 ± 1 Viscosity (cP) 6000 ± 1000 200 ± 100 Form Insertion Time (seconds) 130 ± 65  130 ± 65  Dwell Time (seconds)  0 + 20  0 + 20 Form Retraction Time (seconds) 130 ± 65  130 ± 65  Example 2 DuPont Polyurethane D10M D10M-A Bath Temperature (° C.) 30 ± 5  30 ± 5  Percentage of Solids 12 ± 1  12 ± 1  Viscosity (cP) 3000 ± 1000 3000 ± 100  Form Insertion Time (seconds) 130 ± 65  130 ± 65  Dwell Time (seconds)  0 + 20  0 + 20 Form Retraction Time (seconds) 130 ± 65  130 ± 65 

[0018] In Example 1, the inner layer is minimized in its thickness relative to the total thickness of the finished glove, whereby the properties of the outer layer predominate in the finished glove. In Example 2, the thicknesses of the inner and outer layers are similar in the finished glove, whereby the properties of the inner and outer layers are blended in the finished glove.

[0019] The coefficient of friction of a polyurethane, as used to produce a polyurethane glove, can be measured by placing a sample of the polyurethane, as a sheet, under a weight (e.g., two ounces, Avoirdupois) on a macroscopically smooth, non-reflective, thirty-six inch, steel rule, which rested at one of its ends, on a horizontal surface, and which is elevated gradually at its other end, until the sample and the weight exceed their angle of repose and begin to slide down the steel rule. As measured in units of length, the vertical measure of the triangle formed by a straight line along the steel rule, by a straight line along the horizontal surface, and by a vertical line dropped from the straight line at the elevated end of the steel rule to the straight line along the horizontal surface, is a measure of the coefficient of friction. However, if the sample and the weight do not begin to slip when the steel rule becomes vertical, the coefficient of friction is regarded as too great to be thus measured and the sample is regarded as adhesive. 

1. A process for producing a polymeric glove, wherein the process comprises steps of (a) dipping a glove form into a first bath containing a solvent and a first polymer, which when solidified has a first property, and solidifying the first polymer, (b) dipping the glove form, on which the first polymer has solidified, into a second bath containing a solvent and a second polymer, which when solidified has a second property differing from the first property, and solidifying the second polymer, wherein the solvent of the second batch is capable of solubalizing the first polymer, and (c) stripping what results from the preceding steps, from the glove form, so as to invert what results therefrom, whereby a polymeric glove is produced, which has an outer layer having the first property, an inner layer having the second property, and an intermediate, transitional layer, which results from the first polymer having been partially solubalized by the solvent of the second bath.
 2. A process for producing a polymeric glove, wherein the process comprises steps of (a) dipping a glove form into a first bath containing a solvent and a first polymer, which when solidified has a comparatively lower stiffness, and solidifying the first polymer, (b) dipping the glove form, on which the first polymer has solidified, into a second bath containing a solvent and a second polymer, which when solidified has a comparatively higher stiffness, and solidifying the second polymer, wherein the solvent of the second batch is capable of solubalizing the first polymer, and (c) stripping what results from the preceding steps, from the glove form, so as to invert what results therefrom, whereby a polymeric glove is produced, which has an outer layer having the comparatively lower stiffness, an inner layer having the comparatively higher stiffness, and an intermediate, transitional layer, which results from the first polymer having been partially solubalized by the solvent of the second bath.
 3. A process for producing a polymeric glove, wherein the process comprises steps of (a) dipping a glove form into a first bath containing a solvent and a first polymer, which when solidified has a comparatively higher coefficient of friction, and solidifying the first polymer, (b) dipping the glove form, on which the first polymer has solidified, into a second bath containing a solvent and a second polymer, which when solidified has a comparatively lower coefficient of friction, wherein the solvent of the second batch is capable of solubalizing the first polymer, and solidifying the second polymer, and (c) stripping what results from the preceding steps, from the glove form, so as to invert what results therefrom, whereby a polymeric glove is produced, which has an outer layer defining an outer surface having the comparatively higher coefficient of friction, an inner layer defining an inner surface having the comparatively lower coefficient of friction, and an intermediate, transitional layer, which results from the first polymer having been partially solubalized by the solvent of the second bath.
 4. A process for producing a polymeric glove, wherein the process comprises steps of (a) dipping a glove form into a first bath containing a solvent and a first polymer, which when solidified has a comparatively greater elasticity, and solidifying the first polymer, (b) dipping the glove form, on which the first polymer has solidified, into a second bath containing a solvent and a second polymer, which when solidified has a comparatively lesser elasticity, wherein the solvent of the second batch is capable of solubalizing the first polymer, and solidifying the second polymer, and (c) stripping what results from the preceding steps, from the glove form, so as to invert what results therefrom, whereby a polymeric glove is produced, which has an outer layer having a comparatively greater elasticity, an inner layer having a comparatively lesser elasticity, and an intermediate, transitional layer, which results from the first polymer having been partially solubalized by the solvent of the second bath.
 5. The process of claim 1, 2, 3, or 4 wherein the solvent of the first bath and the solvent of the second bath are similar.
 6. The process of claim 1, 2, 3, or 4 wherein the first and second polymers are polyurethanes.
 7. The process of claim 1, 2, 3, or 4 wherein the first and second polymers are polurethanes and wherein the solvent of the first bath and the solvent of the second bath are similar, each being dimethyl acetimide or dimethyl formamide.
 8. A polymeric glove, which is made by the process of claim
 1. 9. A polymeric glove, which is made by the process of claim
 2. 10. A polymeric glove, which is made by the process of claim
 3. 11. A polymeric glove, which is made by the process of claim
 4. 12. A polymeric glove, which is made by the process of claim
 5. 13. A polymeric glove, which is made by the process of claim
 6. 14. A polymeric glove, which is made by the process of claim
 7. 